Selective harmonic elimination in seven level cascaded inverter

This paper aims to extend the knowledge about the implementation of selective harmonic elimination in cascaded multilevel inverter to eliminate the specified harmonics in the output voltage. An optimization technique is proposed to compute switching angles at fundamental frequency switching scheme by solving non-linear transcendental equations (known as selective harmonic elimination equations), thereby eliminating certain predominating lower order harmonics, and simultaneously, control over magnitude of output voltage of a multilevel inverter is achieved. An experimental 7-level cascaded multilevel inverter using 2 H-bridges was used to implement the algorithm and to validate the methods. A systematic analysis and algorithm based off-line pre-calculation of switching angle for a range of modulation index using Newton Raphson have been implemented. The angles obtained were fed as gate pulse to the switches using ATMEGA328P-PU. The experimental results show that the method can effectively eliminate the specific harmonics as expected.